PBO, introduced by Bailey, Borwein, López de Prado and Zhu, treats strategy selection itself as the thing to validate. It repeatedly splits the data, picks the configuration that looks best in-sample, then checks how that same configuration ranks out-of-sample. If the in-sample winner routinely lands in the bottom half out-of-sample, your selection process is overfitting.
The output is a probability in [0, 1]. Low PBO means the configuration that wins in testing tends to keep winning on unseen data; high PBO (above ~0.5) means your 'best' settings are likely a product of luck and trying many combinations. It is the natural companion to walk-forward testing.
Exemple
After scanning 200 parameter sets, the top set shows a PBO of 0.6 — more likely than not curve-fit — so it is rejected despite a great in-sample Sharpe.
Comment Noon Barbari utilise Probability of Backtest Overfitting (PBO)
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Validate a strategy in noonbarbari →Termes liés
- Backtesting
Overfitting
Fitting a strategy so closely to past data that it captures noise, not signal.
- Backtesting
Walk-forward optimization
Optimize on a rolling in-sample window, validate on the next out-of-sample slice.
- Backtesting
Out-of-sample
Data the strategy was not allowed to see during parameter selection.
- Statistiques
Sharpe ratio
Excess return over the risk-free rate per unit of total volatility.